JPH04293514A - Method and device for removing very small amount of hydrogen from inert gas - Google Patents

Abstract

PURPOSE:To efficiently remove a very small amt. of hydrogen from an inert gas by bringing the inert gas contg. a very small amt. of hydrogen into contact with a silver ion exchange zeolite having oxygen previously coordinated thereto at normal temp. CONSTITUTION:An oxygen-coordinated, silver ion exchange zeolite in a reaction cylinder 1 and an inert gas contg. a very small amt. of hydrogen (e.g. helium) are brought into contact with each other at a temp. of at most 100 deg.C. As a result, the very small amt. of hydrogen can be efficiently removed from the inert gas. In this way the concn. of hydrogen in a purified gas is kept within the identification limit. At this time, the produced water is absorbed immediately by the zeolite skeleton to avoid its mixing in the purified gas. Furthermore, the very small amt. of hydrogen contained in the inert gas reacts with oxygen merely stoichiochemically and, since oxygen is not released from the oxygen- coordinated, silver ion exchange zeolite in the absence of hydrogen participating in a reaction with oxygen, there is no possibility of oxygen being mixed in the purified gas.

Description

Description: TECHNICAL FIELD The present invention relates to a method for efficiently removing trace amounts of hydrogen from an inert gas and an apparatus therefor. [0002] In many manufacturing processes, rare gases such as helium, neon, argon, krypton, and xenon, and inert gases such as nitrogen are often required to be of high purity. Particularly in the manufacture of semiconductor devices, extremely high purity inert gases are required. Commercially available industrial rare gases contain impurity components such as hydrocarbons, carbon monoxide, carbon dioxide, oxygen, nitrogen, hydrogen, and water, and industrial nitrogen gas also contains hydrocarbons. , carbon monoxide, carbon dioxide, oxygen, hydrogen, water, and other impurities, these impurities must be removed to achieve high purity. [0004] In order to obtain highly pure inert gas, various purification methods are employed depending on the types of impurities contained in the inert gas. For example, a method has been adopted in which oxygen and carbon monoxide are removed by an oxidation reaction of nickel. Hydrocarbons are converted into carbon dioxide and water by a combustion reaction using palladium as a catalyst, and the carbon dioxide and water that were originally mixed are removed by contacting with an adsorbent such as molecular sieve. Among these methods, the method of converting hydrocarbons in an inert gas into carbon dioxide and water by a combustion reaction using palladium as a catalyst requires coexisting oxygen or newly added oxygen; Since it is usually difficult to react just the right amount with oxygen, it is necessary to create a complex system that further removes excess oxygen. [0006] Furthermore, in the above-mentioned method of removing oxygen and carbon monoxide by the oxidation reaction of nickel, and the method of converting hydrocarbons into carbon dioxide and water by the combustion reaction using palladium as a catalyst, inert nitrogen-containing High purity gas cannot be obtained. [0007] Therefore, as a method for purifying an inert gas containing nitrogen as an impurity, a method using a single metal or various alloy getter mainly composed of titanium or zirconium has been developed. A reaction tube filled with this getter can simultaneously remove nitrogen, hydrocarbons, carbon monoxide, carbon dioxide, oxygen, hydrogen, and water at high temperatures. However, in the method using a getter, the reaction column is operated at a high temperature, which is an unfavorable condition for hydrogen absorption. can only be purified to a level of several 10 ppb to 100 ppb. [0009] As a measure to improve this point, Japanese Unexamined Patent Application Publication No. 2002-
Inventions described in JP-A No. 116607 and JP-A-2-293310 are known. That is, in JP-A-2-116607, impurities other than hydrogen in the inert gas such as nitrogen, oxygen, moisture, methane, and
Carbon monoxide and carbon dioxide are removed, and only hydrogen is removed by the second-stage getter tube. In this case, the temperature of both the first-stage getter cylinder and the second-stage getter cylinder is set to 350 to 400°C. Furthermore, in JP-A-2-293310, impurities other than hydrogen in a rare gas such as hydrocarbons, nitrogen, oxygen, water,
Methane, carbon monoxide, and carbon dioxide are removed, and then the hydrogen is converted to water at a temperature below 40°C using a nickel-based catalyst packed in the upper part of the second-stage packed cylinder. Moisture is adsorbed by molecular sieves filled in. Problems to be Solved by the Invention As semiconductors become more highly integrated, the purity level required in the manufacture of VLSIs is becoming lower than 1 ppb for each impurity concentration. However, when using a reaction tube filled with a getter, the hydrogen removal rate at high temperatures is not sufficient, and further improvement is required to remove low concentration hydrogen. [0013] In the above-mentioned Japanese Patent Application Laid-Open No. 2-116607, a zirconium-aluminum alloy getter is provided at the latter stage of the getter-packed cylinder for the purpose of removing hydrogen. Adsorption and desorption of hydrogen occurs reversibly and does not reach a sufficient removal level. In Japanese Patent Application Laid-open No. 2-293310, as mentioned above, hydrogen is converted into water at a temperature below 40° C. using a catalyst mainly composed of nickel packed in the upper part of the second stage packing cylinder, and Moisture is adsorbed by molecular sieves packed at the bottom of the second stage packing cylinder, but the level of hydrogen removal in this case is not necessarily satisfactory (in the example, the hydrogen concentration in the raw gas is 1
ppm, the hydrogen concentration in the purified gas is 30 ppb or less), and there is also the hassle of having to further dispose a molecular sieve in order to remove the generated moisture. [0015] Also, in both JP-A-2-116607 and JP-A-2-293310,
When it absorbs a certain amount of hydrogen and loses its capacity, the filling must be replaced with a new one or regenerated, but since the usage status of the filling cannot be confirmed at first glance, the outlet is purified gas. There is a problem in that the timing of replacement or regeneration must be determined by analyzing the gas. [0015] Against this background, the present invention provides an industrial method that can irreversibly remove trace amounts of hydrogen contained in an inert gas at low temperatures and that allows easy confirmation of usage conditions. The purpose is to [Means for Solving the Problems] The method for removing trace amounts of hydrogen of the present invention involves bringing an inert gas containing a trace amount of hydrogen into contact with a silver ion-exchanged zeolite that has been previously coordinated with oxygen at a temperature of 100° C. or lower. This is a characteristic feature. Further, the trace hydrogen removal device of the present invention includes a reaction column (1) filled with silver ion-exchanged zeolite, a gas inlet (2) for introducing gas into the reaction column (1), and a reaction column (1). 1) Gas outlet (3) for extracting gas from
It is equipped with the following. In this case, a heating mechanism (4) may be further provided to heat the silver ion-exchanged zeolite filled in the reaction column (1) for oxygen coordination or regeneration. The present invention will be explained in detail below. Examples of inert gases applicable to the method of the present invention include rare gases such as helium, neon, argon, krypton, and xenon, and nitrogen. Inert gases that contain trace amounts of hydrogen are gases that still contain hydrogen after removing impurity components such as carbon monoxide, carbon dioxide, oxygen, nitrogen, hydrogen, and water from industrial gases, and which do not contain trace amounts of water. It's okay to be there. These impurities may be removed prior to contacting with the oxygen-coordinated silver ion-exchanged zeolite according to the method of the invention. Silver ion exchange zeolite is Mex (Al
At least a portion, especially 10 to 98% or more, of the alkali metal ion (Me) portion of zeolite having the molecular formula O2)y(SiO2)z is ion-exchanged with silver ions. Zeolites include X type, Y type
A variety of zeolites are used, including type A, type A, and type ZSM-5. The silver ions in this silver ion-exchanged zeolite take in oxygen at a slow rate at room temperature, but at a fast rate at around 300°C. Furthermore, at low temperatures, silver ions give the incoming oxygen the oxygen they have taken in beforehand,
Accelerates the reaction that converts to water. Therefore, silver ion-exchanged zeolite is brought into contact with an inert gas containing oxygen at a temperature of around 300°C to bring it into an oxidized state in which oxygen is coordinated, and this is
After returning the temperature to below 0°C, it is brought into contact with an inert gas containing hydrogen. The temperature is set at 100° C. or lower in order to prevent water from being re-desorbed, and the temperature is usually 80° C. or lower, further 60° C. or lower, particularly around room temperature, or even lower. Upon contact with the oxygen-coordinated silver ion-exchanged zeolite, hydrogen in the inert gas is oxidized and converted to water. The generated water is immediately adsorbed to the zeolite skeleton, so
The water concentration in the purified gas will not increase. Furthermore, since the reaction between hydrogen and oxygen is an irreversible reaction due to chemical oxidation and adsorption, there is no risk of hydrogen being re-desorbed due to changes in temperature, flow rate, pressure, etc. As hydrogen in the inert gas is removed, oxygen in the oxygen-coordinated silver ion-exchanged zeolite is gradually lost, and the color changes from white to black. Since the hydrogen removal ability is lost after a certain amount of hydrogen is removed, it is necessary to regenerate the oxygen-coordinated silver ion exchange zeolite at an appropriate stage before it becomes deactivated. This regeneration can be easily achieved by heat-treating the oxygen-coordinated silver ion-exchanged zeolite whose hydrogen removal ability has decreased in an oxygen-containing inert gas stream. The heating temperature is preferably about 250 to 400°C, but is not necessarily limited to this range. Instead of regenerating oxygen-coordinated silver ion-exchanged zeolites,
It can also be made disposable and replaced with other new oxygen-coordinated silver ion-exchanged zeolites. Whether to recycle or make it disposable is determined by scale and other factors. The apparatus for carrying out the above method includes a reaction column (1) filled with silver ion-exchanged zeolite, and a gas inlet (2) for introducing gas into the reaction column (1).
and a gas outlet (
3) A device equipped with the following is used. In this case, a heating mechanism (4) for heating the silver ion exchange zeolite filled in the reaction column (1) for oxygen coordination or regeneration is further provided.
) can be provided. Alternatively, two such reaction columns (1) may be provided in parallel, and while one is removing hydrogen in the inert gas, the other may be regenerated or replaced. [0025] The reaction column (1) has an observation window (5) for identifying the change in color of the oxygen-coordinated silver ion-exchanged zeolite.
It is desirable to provide a replacement time determination sensor (6) for detecting a change in the color of the oxygen-coordinated silver ion-exchanged zeolite. In order to remove various impurities contained in the inert gas, a getter such as titanium, zirconium, zirconium-iron, titanium-zirconium, zirconium-vanadium-iron, etc. is installed on the upstream side of the reaction column (1). It is also possible to install a getter cylinder filled with [Operation] Since oxygen-coordinated silver ion-exchanged zeolite is used in the present invention, hydrogen in the inert gas can be exchanged with oxygen even at room temperature due to the action of oxygen coordinated to the silver ions introduced by ion exchange. reacts and is converted to water. Moreover, a trace amount of hydrogen contained in the inert gas only reacts with oxygen stoichiometrically, and if hydrogen, which is a component to be reacted, is not present, oxygen is removed from the oxygen-coordinated silver ion-exchanged zeolite. Not released. [0029] Since the skeleton is zeolite, water produced by the reaction of hydrogen and oxygen is immediately adsorbed by the zeolite. [0030] As described above, the oxygen-coordinated silver ion exchange zeolite has two functions: the function of converting hydrogen into water and the function of adsorbing the generated water, and these functions are more than 100% It is exhibited at low temperatures below ℃ (for example, room temperature). In addition, this oxygen-coordinated silver ion exchange zeolite recovers its hydrogen removal ability by heating it in the presence of oxygen after removing a certain amount of hydrogen. [Example] Next, the present invention will be further explained with reference to Examples. Embodiment 1 FIG. 1 is an explanatory diagram showing an example of the removal apparatus of the present invention. [0034] (1) is a reaction cylinder, with an outer diameter of 38.1 m.
m, inner diameter 32.6 mm, and height 127 mm. (2) is the gas inlet for introducing inert gas, (3)
is a gas outlet that leads out gas from the reaction tube (1), (5)
is a transparent observation window, (7) is a flow rate control device, (8
) is a gas filter for particle removal. [0035] A spherical silver ion-exchanged zeolite with a diameter of 1.5 mm (zeolite used is X-type zeolite) in which 50% of sodium ions were ion-exchanged with silver ions was heated at 300°C using argon gas with an oxygen concentration of 20%. After performing thermal oxidation to coordinate oxygen, the mixture was allowed to cool to room temperature. As a result, the silver ion-exchanged zeolite was oxidized and became an oxygen-coordinated silver ion-exchanged zeolite. 75 cc of this oxygen-coordinated silver ion-exchanged zeolite was packed into the reaction column (1). [0036] Next, 1.3p was introduced into the reaction column (1) via the flow rate control device (7) and the gas inlet (2).
Argon gas containing pm hydrogen at 2 liters/min
, 1 atm, and was led out from the gas outlet (3). The hydrogen concentration in the purified gas derived from the gas outlet (3) was measured using a gas chromatograph mass spectrometer (QP-300) manufactured by Shimadzu Corporation. Table 1 shows the results.
Shown below. At the same time, the outlet moisture concentration was measured using a crystal oscillation moisture meter (MAH-2) manufactured by Shimadzu Corporation, and the dew point of the purified gas was -98°C or lower. Table 1 Impurity name Inlet concentration
Outlet concentration detection limit
hydrogen
1.3 ppm below detection limit
5 ppb 0038
]The color of the oxygen-coordinated silver ion-exchanged zeolite in the reaction tube (1) changes from white to black due to the reaction with hydrogen in the argon gas, and this is monitored through the quartz glass observation window (5). By doing so, you can check the usage status and know when to replace it. Based on the results in Table 1, the cumulative amount of hydrogen removed from argon gas was measured for the following three types of fillers. (a) 50% silver ion exchange zeolite without prior heat oxidation treatment (b) Oxygen-coordinated silver ion exchange zeolite obtained by heat oxidation treatment of (a) above (c) Sufficient for (b) above Oxygen-coordinated silver ion-exchanged zeolite obtained by deactivating it by passing hydrogen through it, and then performing a heating oxidation regeneration treatment at a temperature of 300°C. Namely, a reaction column (1) filled with each of the above-mentioned fillers was charged with 150 ppm. Argon gas containing hydrogen at room temperature was continuously introduced at a flow rate of 1 liter/min, and the hydrogen concentration in the outlet gas led out from the gas outlet (3) was measured. The results are shown in Figure 2. From FIG. 2, it can be seen that when the filler (b) is used, it reaches a breakthrough state in about 8 and a half hours, but when it is regenerated (
Since the filler c) also reached a breakthrough state in about 8 and a half hours, it can be seen that regeneration is almost complete. Note that (a)
, (b), (c) In all cases, the dew point of the outlet gas was -98°C or lower. Embodiment 2 FIG. 3 is an explanatory diagram showing another example of the removal apparatus of the present invention. In Example 1, the purpose was only to remove hydrogen from the inert gas, but in order to simultaneously remove impurities other than hydrogen from the inert gas, a reaction column (
1) A getter tube (9) filled with a titanium or zirconium getter was installed on the upstream side of the inert gas to simultaneously remove nitrogen, oxygen, carbon dioxide, carbon monoxide, methane, and water from the inert gas. The getter filled in the getter cylinder (9) in FIG. 3 is a zirconium getter manufactured by SAES, and after being activated by heating at an initial temperature of 450°C for 2 hours, the getter was heated to 400°C.
methane, carbon monoxide, carbon dioxide, oxygen, and moisture in the inert gas can be removed. Hydrogen can also be removed to a level of 50 to 100 ppb, but in order to further increase the purity of the inert gas, complete hydrogen removal is performed using oxygen-coordinated 98% silver ion exchange zeolite packed in the reaction column (1). did. Note that (10) is a heater, and (11) is a heater case. [0044] The 98% silver ion-exchanged zeolite, which had been oxygen-coordinated by heating and oxidizing it in advance at 300°C using argon gas with an oxygen concentration of 20%, was allowed to cool to room temperature and then filled into the reaction column (1). did. Argon gas containing the impurities shown in Table 2 is supplied from the flow rate control device (7) at 2 liters/min, 1 atm.
After passing through the getter tube (9), the reaction tube (
1) and led out from the gas outlet (3). The results are shown in Table 2. The dew point of the gas is -72℃ at the inlet,
The temperature at the outlet was -98°C or lower. Table 2 Impurity name Inlet concentration
Outlet concentration detection limit
hydrogen
1.3 ppm below detection limit
5 ppb
Carbon dioxide 0.5 ppm
Below detection limit 2 ppb
nitrogen
1.5 ppm below detection limit
4 ppb 0047
In addition, in Example 1, the replacement time was visually determined through the observation window (5) provided in the reaction tube (1), but in this Example 2, the replacement time was determined by recognizing the color. Judgment sensor (6) and reaction tube (1)
attached to the sensor amplifier (6) to automatically determine when to replace it.
The display judgment was made in a). Embodiment 3 FIG. 4 is an explanatory diagram showing still another example of the removal apparatus of the present invention. In Examples 1 and 2 above, when hydrogen in the inert gas is absorbed up to a certain amount, the reaction column (1)
However, when silver ion-exchanged zeolite is heated with oxygen-containing gas, it returns to its initial oxygen-coordinated state and can be reused for hydrogen removal. A regenerative removal device using this property is shown in FIG. In FIG. 4, the inert gas from which oxygen and carbon monoxide have been removed by the nickel in the getter cylinder (9) is converted into hydrogen and carbon dioxide by the oxygen-coordinated 25% silver ion exchange zeolite in the reaction cylinder (1). Carbon and water are removed. Oxygen-coordinated 25% silver ion-exchanged zeolite When a certain amount of impurities are removed, the coordinated oxygen disappears, so a little before that, the valves (12) and (16)
is closed, an inert gas containing oxygen is supplied from the valve (15), and while the reaction column (1) is heated by the heating mechanism (4), the gas from the regeneration is discarded from the valve (14) to produce 25% silver. Oxygen can be recoordinated to the ion-exchanged zeolite. After sufficient regeneration, turn the valve (1
3), (14), (15) and close the valve (12).
, (16), the purification operation can be continued. These series of operations can be performed automatically using a sequencer and can be operated unmanned. [0052] According to the present invention, trace amounts of hydrogen contained in an inert gas can be irreversibly removed to below the detection limit at low temperatures (for example, room temperature), and the generated water can be immediately removed. It is adsorbed on the zeolite skeleton and does not mix into purified gas. Furthermore, at this time, the trace amount of hydrogen contained in the inert gas only reacts stoichiometrically with oxygen, and if hydrogen, which is a component to be reacted, is not present, the oxygen-coordinated silver ion-exchanged zeolite reacts with oxygen. Since oxygen is not released, there is no risk of oxygen being mixed into the purified gas. In addition, as the hydrogen is removed, the color of the oxygen-coordinated silver ion-exchanged zeolite changes from white to black, so the state of use can be easily checked and the timing of replacement or switching will not be mistaken. Therefore, the present invention is revolutionary and extremely useful as an industrial method for removing trace amounts of hydrogen contained in inert gas.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of a removal device of the present invention.

[Figure 2] Shows the relationship between the gas introduction time and the hydrogen concentration in the outlet gas when room temperature argon gas containing 150 ppm hydrogen was continuously introduced into the reaction column (1) at a flow rate of 1 liter/min. The graph shows (a) 50% silver ion-exchanged zeolite, (b) oxygen-coordinated silver ion-exchanged zeolite, and (c) oxygen-coordinated silver ion-exchanged zeolite obtained through regeneration treatment in reaction column (1). The figure shows the case filled with

FIG. 3 is an explanatory diagram showing another example of the removal device of the present invention.

FIG. 4 is an explanatory diagram showing still another example of the removal device of the present invention.

[Explanation of symbols]

(1) ...Reaction tube, (2) ...Gas inlet, (3) ...Gas outlet, (4) ...Heating mechanism, (5) ...Observation window, (6)
...Sensor for determining replacement time, (6a) ...Sensor amplifier, (7) ...Flow rate control device, (8) ...Gas filter, (9) ...Getter cylinder, (10) ...Heater, (1
1)...Heater case, (12), (13), (1
4), (15), (16)...Valve

Claims (6)

[Claims] 1. A method for removing trace amounts of hydrogen, which comprises bringing an inert gas containing trace amounts of hydrogen into contact with silver ion-exchanged zeolite, which has been previously coordinated with oxygen, at 100° C. or lower. 2. The removal method according to claim 1, wherein the oxygen-coordinated silver ion exchange zeolite that has absorbed a certain amount of hydrogen is activated by heat treatment in an inert gas stream containing oxygen. 3. A reaction column (1) filled with silver ion-exchanged zeolite, a gas inlet (2) for introducing gas into the reaction column (1), and a gas outlet (2) for introducing gas from the reaction column (1). 3) A device for removing trace amounts of hydrogen in an inert gas, comprising: 4. A reaction column (1) filled with silver ion-exchanged zeolite, a gas inlet (2) for introducing gas into the reaction column (1), and a gas outlet (2) for introducing gas from the reaction column (1). 3) and a heating mechanism (4) for heating the silver ion-exchanged zeolite filled in the reaction column (1) for oxygen coordination or regeneration. 5. The reaction column (1) has an observation window (5) for identifying a change in color of the oxygen-coordinated silver ion-exchanged zeolite.
5. The removing device according to claim 3, further comprising: 6. The removal device according to claim 3 or 4, wherein the reaction column (1) is provided with a replacement timing determination sensor (6) for detecting a change in color of the oxygen-coordinated silver ion-exchanged zeolite. .